CP/M/CPM_CDROM.iso/mbug/mbug028.arc/SMFORTH1.ASM

Assembly Source File | 1979-12-31 | 22KB | 933 lines

;
;    Minimal Forth-like  interpreter as presented
;    in Kilobaud Magazine, February, 1981
;    issue, page 76    by Richard Fritzson
;
;    Note: this is part 1 of a promised 3-part
;    system, to include a compiler, and, hopefully,
;    an editor.
;
;
;                   02/04/81:
;        typed in by Ron Fowler, Westland, Mich
;        (modified slightly: the original version
;        had I/O routines to BIOS hard-coded, and
;        memory fixed at time of assembly.   Mod-
;        ified for any size CPM, and dynamic  fix
;        of memory size at run time)
;
;
;    if you're not using MAC to assemble this program,
;    delete the next statement:

    TITLE    'Threaded Code Interpreter for 8080'
;
; Richard Fritzson
; 29 January 1980      Version 1.0
;
; This version contains only the basic internal
; interpreter and a simple interactive console
; interpreter.
;
    ORG    100H    ;START UP ADDRESS
;
BASE:    LXI    SP,STACK ;INITIALIZE PARAMETER STACK
    CALL    DICMOVE ;MOVE DICTIONARY TO HIGH MEMORY
    LXI    H,TOP-1 ;SET PC TO TOP LEVEL LOOP
    SHLD    PC
    JMP    NEXT    ;AND START INTERPRETER
;
; TOP - Top Level System Loop
; DESCRIPTION: TOP in an infinite
; loop which picks up the contents of the
; EXEC variable and executes it.
;
TOP:    DW    EXEC,PEEKW    ;GET TOP LEVEL PROGRAM
    DW    EXECUTE     ;RUN IT
    DW    JUMP,TOP-1    ;AND LOOP
;
; EXEC - address of top level routine
;
EXEC:    DW    VARIABLE    ;THREADED CODE VARIABLE
    DW    INTERACT    ;ADDRESS OF USER INTERPRETER
;
; Reserved Stack Space
;
    DS    128        ;PARAMETER STACK
STACK    EQU    $
    PAGE
;
; The interpreter's architecture: a program counter and a stack
;
PC    DW    0    ;A 16 BIT POINTER INTO THE MIDDLE OF
            ;THE CURRENT INSTRUCTION (NOT THE
            ;FIRST BYTE, BUT THE SECOND)
;
RSTACK    DW    $+2    ;THE STACK POINTER POINTS TO THE NEXT
            ;AVAILABLE STACK POSITION (NOT THE
            ;TOPMOST OCCUPIED POSITION)
;
    DS    80H    ;RESERVED STACK SPACE
;
; RPUSH - push DE on stack
; ENTRY: DE - number to be pushed on stack
; EXIT:  DE - is unchanged
; DESCRIPTION: this code is illustrative of how the
; stack works.    However it is not used in the system and
; can be left out.
;
RPUSH:    LHLD    RSTACK    ;GET STACK POINTER
    MOV    M,E    ;STORE LOW BYTE
    INX    H    ;BUMP POINTER TO NEXT BYTE
    MOV    M,D    ;STORE HIGH BYTE
    INX    H    ;BUMP POINTER TO NEXT EMPTY SLOT
    SHLD    RSTACK    ;RESTORE POINTER
    RET
;
; RPOP - pop DE from stack
; ENTRY: No Register Values Expected
; EXIT:  DE - top element of RSTACK
; DESCRIPTION: this code is illustrative of how the
; stack works.    However it is not used in the system and
; can be left out.
;
RPOP:    LHLD    RSTACK    ;GET STACK POINTER
    DCX    H    ;DROP TO FIRST STACK POSITION
    MOV    D,M    ;GET HIGH BYTE
    DCX    H
    MOV    E,M    ;GET LOW BYTE
    SHLD    RSTACK    ;RESTORE STACK POINTER
    RET
;
; NEXT - main internal interpreter loop
; ENTRY: PC - points into the instruction just completed
; EXIT:  PC - incremented by 2, points to next
;          instruction
;     DE - points to middle of first word of
;          next routine (i.e. (PC)+1)
; DESCRIPTION: increments the PC; picks up the code
; word of the next routine and jumps to it.
;
NEXT:    LHLD    PC    ;INCREMENT PROGRAM COUNTER
    INX    H    ;  WHILE LOADING DE WITH
    MOV    E,M    ;  NEXT INSTRUCTION
    INX    H
    MOV    D,M
    SHLD    PC
    XCHG        ;PICK UP WORD ADDRESSED
    MOV    E,M    ;BY NEXT INSTRUCTION (WHICH
    INX    H    ;  IS CODE, TCALL OR SOME OTHER
    MOV    D,M    ;  EXECUTABLE ADDRESS)
    XCHG        ;  AND
    PCHL        ;  JUMP TO IT
;
; TCALL - the threaded call routine
; ENTRY: DE - middle of first word of routine being called
; EXIT:  No Register Values Returned
; DESCRIPTION: pushes the current congtents of the PC
; onto the return stack; makes DE the new PC
;
TCALL:    LHLD    PC    ;GET OLD PROGRAM COUNTER
    XCHG        ;REPLACE WITH DE
    SHLD    PC
    LHLD    RSTACK    ;PUSH OLD PC ON RSTACK
    MOV    M,E
    INX    H
    MOV    M,D
    INX    H
    SHLD    RSTACK
    JMP    NEXT    ;BACK TO INTERPRETER
;
; TRET - the threaded code return
; DESCRIPTION: pops the top element of the
;           return stack and puts it into the PC.
;
TRET:    DW    $+2    ;CODE
    LHLD    RSTACK    ;GET STACK POINTER
    DCX    H    ;HIGH BYTE OF TOP ELEMENT
    MOV    D,M
    DCX    H    ;LOW BYTE OF TOP ELEMENT
    MOV    E,M
    SHLD    RSTACK    ;RESTORE STACK POINTER
    XCHG        ;STORE TOP OF STACK IN PC
    SHLD    PC
    JMP    NEXT    ;BACK TO INTERPRETER
;
; Simple arithmetic routines
;
; INC - increment the top of the stack
;
INC:    DW    $+2    ;CODE
    POP    H    ;GET TOP
    INX    H    ;INCREMENT
    PUSH    H    ;RESTORE
    JMP    NEXT
;
; DEC - decrement the top of the stack
;
DEC:    DW    $+2    ;CODE
    POP    H    ;GET TOP
    DCX    H    ;DECREMENT
    PUSH    H    ;RESTORE
    JMP    NEXT
;
; TADD - add the top two elements of the stack
;
TADD:    DW    $+2    ;CODE
    POP    H    ;FIRST ELEMENT
    POP    D    ;SECOND ELEMENT
    DAD    D    ;ADD 'EM
    PUSH    H    ;PUSH RESULT
    JMP    NEXT
;
; MINUS - negate top of stack
;
MINUS:    DW    $+2    ;CODE
    POP    H    ;GET TOP
    CALL    MINUSH    ;NEGATE IT
    PUSH    H    ;PUSH IT
    JMP    NEXT
;
MINUSH: DCX    H    ;GOOD OLE 2S COMPLEMENT
    MOV    A,H
    CMA
    MOV    H,A
    MOV    A,L
    CMA
    MOV    L,A
    RET
;
; TSUB - subtract TOP from TOP-1
;
TSUB:    DW    TCALL    ;THREADED CODE
    DW    MINUS    ;NEGATE TOP
    DW    TADD    ;AND ADD
    DW    TRET
;
; PEEKB - retrieve a byte from memory
; ENTRY: TOP - address
; EXIT:  TOP - byte at address
;
PEEKB:    DW    $+2    ;CODE
    POP    H    ;GET ADDRESS
    MOV    E,M    ;GET BYTE
    MVI    D,0
    PUSH    D    ;SAVE
    JMP    NEXT
;
; PEEKW - retrieve a word from memory
; ENTRY: TOP - address
; EXIT:  TOP - word at address
;
PEEKW:    DW    $+2    ;CODE
    POP    H    ;GET ADDRESS
    MOV    E,M    ;GET WORD
    INX    H
    MOV    D,M
    PUSH    D    ;SAVE
    JMP    NEXT
;
; POKEB - store byte in memory
; ENTRY: TOP - address
;     TOP-1 - byte to store
; EXIT:  No Values Returned
;
POKEB:    DW    $+2    ;CODE
    POP    H    ;GET ADDRESS
    POP    D    ;GET BYTE
    MOV    M,E    ;STORE
    JMP    NEXT
;
; POKEW - store word in memory
; ENTRY: TOP - address
;     TOP-1 - word to store
; EXIT: No Values returned
;
POKEW:    DW    $+2    ;CODE
    POP    H    ;GET ADDRESS
    POP    D    ;GET WORD
    MOV    M,E    ;STORE WORD
    INX    H
    MOV    M,D
    JMP    NEXT
;
; Some standart threaded code functions
; TPUSH - push the next word onto the stack
;
TPUSH:    DW    $+2    ;CODE
    LHLD    PC    ;GET PROGRAM COUNTER
    INX    H    ;ADVANCE TO NEXT WORD
    MOV    E,M    ;AND PICK UP CONTENTS
    INX    H
    MOV    D,M
    SHLD    PC    ;STORE NEW PROGRAM COUNTER
    PUSH    D    ;PUSH WORD ONTO PARAM STACK
    JMP    NEXT    ;CONTINUE
;
; TPOP - drop the top of the parameter stack
;
TPOP:    DW    $+2    ;CODE
    POP    H    ;POP ONE ELEMENT
    JMP    NEXT    ;  AND CONTINUE
;
; SWAP - exchange top two elements of the stack
;
SWAP:    DW    $+2    ;CODE
    POP    H    ;GET ONE ELEMENT
    XTHL        ;XCHG
    PUSH    H    ;PUT BACK
    JMP    NEXT    ;AND CONTINUE
;
; DUP - duplicate the top of the stack
; DESCRIPTION: often used before functions which
; consume the top of the stack (e.g. conditional jumps)
;
DUP:    DW    $+2    ;CODE
    POP    H    ;GET TOP
    PUSH    H    ;SAVE IT TWICE
    PUSH    H
    JMP    NEXT
;
; CLEAR - clear the stack
;
CLEAR:    DW    $+2    ;CODE
    LXI    SP,STACK ;RESET STACK POINTER;
    JMP    NEXT
;
; Threaded Code Jumps
;
; All Jumps are to absolute locations
; All Conditional jumps consume the
; elements of the stack that they test
;
; JUMP - unconditional jump
;
JUMP:    DW    $+2    ;CODE
JUMP1:    LHLD    PC    ;GET PROGRAM COUNTER
    INX    H    ;GET NEXT WORD
    MOV    E,M
    INX    H
    MOV    D,M
    XCHG        ;MAKE IT THE PC
    SHLD    PC
    JMP    NEXT
;
; IFZ - jump if top is zero
;
IFZ:    DW    $+2    ;CODE
    POP    H    ;GET TOP
    MOV    A,H    ;TEST FOR ZERO
    ORA    L
    JZ    JUMP1    ;IF YES, JUMP
SKIP:    LHLD    PC    ;ELSE SIMPLY SKIP NEXT WORD
    INX    H
    INX    H
    SHLD    PC
    JMP    NEXT
;
; IFNZ - jump if top not zero
;
IFNZ:    DW    $+2    ;CODE
    POP    H    ;GET TOP
    MOV    A,H    ;TEST FOR ZERO
    ORA    L
    JNZ    JUMP1    ;IF NOT, JUMP
    JMP    SKIP    ;ELSE DON'T
;
; IFEQ - jump if TOP = TOP-1
;
IFEQ:    DW    $+2    ;CODE
    POP    H    ;GET TOP
    CALL    MINUSH    ;NEGATE IT
    POP    D    ;GET TOP-1
    DAD    D    ;ADD 'EM
    MOV    A,H    ;TEST FOR ZERO
    ORA    L
    JZ    JUMP1    ;IF EQUAL, JUMP
    JMP    SKIP    ;IF NOT, DON'T
;
; Implementation of Constants and Variables in a
; threaded code system
;
 ;CONSTANT - code address for constants
; ENTRY: DE - points to middle of code word for
;          constant
; DESCRIPTION: picks up the contents of the word
; following the code word and pushes it onto the stack.
;
CONSTANT:
    XCHG        ;HL <- ADDRESS OF CODE WORD
    INX    H    ;GET CONSTANT
    MOV    E,M
    INX    H
    MOV    D,M
    PUSH    D    ;PUSH IT ON THE PARAMETER STACK
    JMP    NEXT    ;RETURN TO INTERPRETER
;
; Some common constants
;
ZERO:    DW    CONSTANT    ;THREADED CODE CONSTANT
    DW    0
;
ONE:    DW    CONSTANT    ;THREADED CODE CONSTANT
    DW    1
;
NEGONE: DW    CONSTANT    ;THREADED CODE CONSTANT
    DW    -1
;
MEMORY: DW    CONSTANT    ;LAST AVAILABLE BYTE
    DW    8*1024-1    ;8K SYSTEM
;
; VARIABLE - code address for variables
; ENTRY: DE - points to middle of code word for
;          variable
; DESCRIPTION: pushes address of word following code
;           word onto the stack
;
VARIABLE:
    INX    D    ;INCREMENT TO VARIABLE ADDRESS
    PUSH    D    ;STORE ON PARAMETER STACK
    JMP    NEXT    ;RETURN TO INTERPRETER
;
; Top Level External Interpreter Version 1.0
;
; This routine reads one line of reverse
; polish notation from the console and executes it.
;
INTERACT:
    DW    TCALL        ;THREADED CODE
;
    DW    PROMPT        ;PROMPT THE USER AND
    DW    READLINE    ;READ A CONSOLE LINE
;
SLOOP:    DW    SCAN        ;SCAN FOR NEXT WORD
    DW    IFZ,EXIT-1    ;IF END OF LINE, QUIT
    DW    LOOKUP        ;ELSE LOOKUP WORD IN DICTIONARY
    DW    IFZ,NUMBER-1    ;IF NOT FOUND, TRY NUMBER
    DW    EXECUTE     ;ELSE EXECUTE IT
    DW    JUMP,SLOOP-1    ;AND CONTINUE SCANNING
;
NUMBER: DW    CONAXB        ;TRY CONVERTING TO NUMBER
    DW    IFNZ,SLOOP-1    ;IF SUCCESSFUL, LEAVE ON STACK
                ;AND CONTINUE SCANNING
    DW    TPUSH,ERRMSG    ;ELSE PUSH ERROR MESSAGE
    DW    PRINTS        ;AND PRINT IT
    DW    PRINTS        ;THEN PRINT STRING
    DW    TRET        ;AND RETURN
;
EXIT:    DW    DUP,CONBXA    ;COPY AND CONVERT TOP OF STACK
    DW    PRINTS        ;PRINT IT
    DW    TRET        ;RETURN
;
ERRMSG: DB    13,'Not Defined: '
;
; LOOKUP - the dictionary lookup routine
; ENTRY: TOP  -  pointer to string to be looked up
; EXIT:  TOP  -  -1 if string found in dictionary
;          0 if string not found
;     TOP-1 - pointer to code of found subroutine
;            or
;         string pointer if not found
; DESCRIPTION: performs a linear search of the
; dictionary. Returns the code address if the string
; is found, or else the string pointer if not found
;
LOOKUP: DW    TCALL        ;THREADED CODE
    DW    NAMES,PEEKW    ;GET TOP OF DICTIONARY
;
SEARCH: DW    DUP,PEEKB    ;GET CHAR COUNT OF NEXT ENTRY
    DW    IFZ,FAIL-1    ;IF END OF DICTIONARY
;
    DW    MATCH        ;ELSE ATTEMPT A MATCH
    DW    IFNZ,SUCCEED-1    ;IF SUCCESSFUL MATCH
;
    DW    FIRST,TADD    ;ELSE SKIP STRING
    DW    TPUSH,2,TADD    ;AND POINTER
    DW    JUMP,SEARCH-1    ;AND TRY NEXT ENTRY
;
FAIL:    DW    TPOP        ;DROP DICTIONARY POINTER
    DW    ZERO        ;LEAVE A ZERO ON THE STACK
    DW    TRET        ;AND QUIT
;
SUCCEED:
    DW    SWAP,TPOP    ;DROP STRING POINTER
    DW    FIRST,TADD,PEEKW ;GET CODE POINTER
    DW    NEGONE        ;PUSH A MINUS ONE
    DW    TRET        ;AND RETURN
;
; Names - address of dictionary names
;
NAMES:    DW    VARIABLE    ;THREADED CODE VARIABLE
    DW    NAMEBEG     ;BEGINNING OF NAMES
;
; MATCH - match strings
; ENTRY: TOP   - ptr to string
;     TOP-1 - ptr to another string
; EXIT:  TOP   - -1 if strings are the same
;          0 if strings do not match
;     TOP-1 - ptr to first string
;     TOP-2 - ptr to second string
; DESCRIPTION: written in assembly to speed things up
;
MATCH:    DW    $+2        ;CODE
    POP    H        ;FIRST STRING
    POP    D        ;SECOND STRING
    PUSH    D        ;LEAVE ON STACK
    PUSH    H
    LDAX    D        ;GET 2ND COUNT
    CMP    M        ;COMPARE WITH FIRST
    JNZ    MATCHF        ;IF NO MATCH
                ;ELSE TRY STRING MATCHING
    MOV    B,A
MATCH1: INX    H        ;NEXT BYTE
    INX    D
    LDAX    D
    CMP    M
    JNZ    MATCHF        ;IF NO MATCH
    DCR    B        ;ELSE DEC COUNT
    JNZ    MATCH1        ;IF MORE TO COMPARE
    LXI    H,-1        ;ELSE PUSH SUCCESS
    PUSH    H
    JMP    NEXT
;
MATCHF: LXI    H,0        ;FAILURE
    PUSH    H
    JMP    NEXT
;
; EXECUTE - execute routine at top of stack
; ENTRY: TOP  - address of routine to be executed
; EXIT:  DE   - middle of word addressed by top
; DESCRIPTION: The address is of a threaded code
; interpreter routine, so the contents of the
; first word is an executable address. EXECUTE
; gets that address and jumps to it, leaving DE
; in the same state that the main interpreter
; loop (NEXT) would have.
;
EXECUTE:
    DW    $+2        ;CODE
    POP    H        ;GET ADDRESS
    MOV    E,M        ;GET FIRST WORD
    INX    H
    MOV    D,M
    XCHG            ;AND JUMP TO IT
    PCHL
;
; READLINE - fill console buffer
; DESCRIPTION: reads characters from the console, echoing them
; to the screen and storing them in the console buffer,
; beginning in the third character of the buffer.
; Stops on encountering a carriage return and stores a
; final zero after the other characters.
; Takes appropriate action for a backspace character.
;
READLINE:
    DW    TCALL        ;THREADED CALL
    DW    ZERO        ;MARK BUFFER AS UNSCANNED
    DW    CONBUF,POKEB
;
    DW    CONBUF,INC,INC    ;PUSH FIRST BYTE OF BUFFER
;
RLOOP:    DW    DUP        ;DUPLICATE BUFFER POINTER
    DW    CIN        ;GET CHARACTER
    DW    DUP,COUT    ;ECHO TO SCREEN
;
    DW    DUP,TPUSH,08H    ;COMPARE WITH BACKSPACE
    DW    IFEQ,BKSP-1
;
    DW    DUP,TPUSH,0DH    ;COMPARE WITH CARRIAGE RETURN
    DW    IFEQ,EOL-1
;
    DW    SWAP,POKEB    ;IF NEITHER, STORE IN BUFFER
    DW    INC        ;INCREMENT BUFFER POINTER
    DW    JUMP,RLOOP-1    ;AND KEEP READING
;
BKSP:    DW    TPOP,TPOP    ;DROP BS AND BUFFER PTR COPY
    DW    DEC        ;BACKUP POINTER
    DW    TPUSH,20H,COUT    ;PRINT A SPACE
    DW    TPUSH,08H,COUT    ;AND ANOTHER BACKSPACE
    DW    JUMP,RLOOP-1
;
EOL:    DW    TPOP,TPOP    ;DROP CR AND BUFFER PTR COPY
    DW    ZERO,SWAP,POKEB ;STORE FINAL ZERO
    DW    TPUSH,0AH,COUT    ;PRINT A LINE FEED
    DW    TRET        ;AND RETURN
;
; Console Buffer
; DESCRIPTION: First byte contains the scan pointer which
; points to the next byte to be scanned. The remaining bytes
; contain characters read from the console.
;
CONBUF: DW    VARIABLE    ;THREADED CODE VARIABLE
    DS    101D        ;LONG ENOUGH FOR MOST SCREENS
;
; PROMPT - prompt the user
; DESCRIPTION: clears to a new line and prints a hyphen
;
PROMPT: DW    TCALL        ;THREADED CODE
    DW    TPUSH,PRMSG    ;PUSH PROMPT MESSAGE
    DW    PRINTS        ;AND PRINT IT
    DW    TRET
;
PRMSG:    DB    3,0DH,0AH,'-'
;
; PRINTS - prints string
; ENTRY: TOP  - points to string
; DESCRIPTION: Uses first byte of string as a character count
;
PRINTS: DW    TCALL        ;THREADED CODE
    DW    FIRST        ;GET COUNT
PRINTS1:
    DW    DUP,IFZ,PRINTX-1 ;IF DONE RETURN
    DW    SWAP,FIRST    ;ELSE GET NEXT CHARACTER
    DW    COUT        ;PRINT IT
    DW    SWAP,DEC    ;DECREMENT COUNT
    DW    JUMP,PRINTS1-1    ;AND KEEP LOOPING
;
PRINTX: DW    TPOP,TPOP    ;DROP COUNT AND POOINTER
    DW    TRET        ;THEN RETURN
;
; FIRST - get next byte of string on stack
; ENTRY: TOP   - ptr to string
; EXIT:  TOP   - first character of string
;     TOP-1 - ptr to rest of string
; DESCRIPTION: useful for advancing through strings a byte
; at a time.
;
FIRST:    DW    $+2        ;CODE
    POP    H        ;GET POINTER
    MOV    C,M        ;BC <- CHARACTER
    MVI    B,0
    INX    H        ;BUMP POINTER
    PUSH    H        ;RESTORE POINTER
    PUSH    B        ;ADD CHARACTER
    JMP    NEXT        ;CONTINUE
;
; COUT - character output routine
; ENTRY: TOP - character to print
; DESCRIPTION: uses operating system to print character
; <<<=== NOTE: MODIFIED FOR VAR. SIZE CPM SYS (RGF) ===>>>
;
COUT:    DW    $+2        ;CODE
    POP    B        ;C <- CHARACTER
VCOUT:    CALL    7E0CH        ;PRINT IT (<<MODIFIED AT INIT>>)
    JMP    NEXT        ;RETURN
;
; CIN - character input routine
; EXIT: TOP  - character read from console
; DESCRIPTION: Uses operating system
; <<<=== NOTE: MODIFIED FOR VAR. SIZE CPM SYS (RGF) ===>>>
;
CIN:    DW    $+2        ;CODE
VCIN:    CALL    7E09H        ;READ CHARACTER ((<<MODIFIED AT INIT>>)
    MOV    L,A        ;HL <- CHARACTER
    MVI    H,0
    PUSH    H        ;PUSH ON STACK
    JMP    NEXT        ;RETURN
;
; SCAN - Scan for next word
; ENTRY: No Values Expected
; EXIT: TOP    -  -1 if word found, 0 if word not found
;    TOP-1  -  ptr to word if found (else nothing)
; DESCRIPTION: first byte of buffer contains a counter of
; characters already scanned. The next word is moved to the
; beginning of the line with a leading byte count.
;
SCAN:    DW    $+2        ;CODE
    LXI    H,CONBUF+2    ;BC <- CHARACTER COUNT
    MOV    C,M
    MVI    B,0
    INR    M        ;TEST FOR END OF LINE ALREADY
    JZ    SCANX        ;IF YES
    INX    H        ;HL <- SCANNING START POINT
    DAD    B
    MOV    B,C        ;B <- CHARACTER COUNT
SCAN1:    INX    H        ;INCREMENT POINTER
    INR    B        ;INCREMENT COUNT
    MOV    A,M        ;GET NEXT CHARACTER
    ORA    A        ;TEST FOR END OF LINE
    JZ    SCANX        ;IF YES,
    CPI    20H        ;ELSE, CHECK FOR BLANK
    JZ    SCAN1        ;IF YES, SKIP IT
    LXI    D,CONBUF+3    ;ELSE BEGIN MOVING WORD
    MVI    C,0        ;C <- SIZE OF STRING
SCAN2:    INX    D
    STAX    D
    INR    C        ;INC WORD SIZE
    INR    B        ;INC SCANNED CHAR COUNT
    INX    H        ;GET NEXT BYTE
    MOV    A,M
    ORA    A        ;TEST FOR END OF LINE
    JNZ    SCAN3        ;IF NOT,
    MVI    B,-1        ;ELSE SET EOL FLAG
    MVI    A,20H        ;AND CHANGE EOL TO DELIMETER
SCAN3:    CPI    20H        ;CHECK FOR SPACE
    JNZ    SCAN2        ;IF NOT YET
    LXI    H,CONBUF+2    ;ELSE SAVE SCANNED CHAR COUNT
    MOV    M,B
    INX    H        ;AND WORD SIZE
    MOV    M,C
    PUSH    H        ;AND RETURN WORD POINTER
    LXI    H,-1
    PUSH    H
    JMP    NEXT
;
SCANX:    MVI    A,-1        ;HIT END OF LINE
    STA    CONBUF+2    ;MARK BUFFER EMPTY
    LXI    H,0        ;RETURN A ZERO
    PUSH    H
    JMP    NEXT
;
; CONBXA - convert binary to ascii
;
; ENTRY: TOP - 16 bit positive integer
; EXIT:  TOP - address of converted ASCII string
; DESCRIPTION: pushes the digits of the number
; on to the stack, least significant digits first.
; Then pops them up and stores them in a local
; buffer.
;
CONBXA: DW    TCALL        ;THREADED CODE
    DW    NEGONE,SWAP    ;MARK END OF STRING WITH -1
CONB1:    DW    TPUSH,10,DIV    ;DIVIDE NUMBER BY 10
    DW    SWAP        ;PUT QUOTIENT ON TOP
    DW    DUP
    DW    IFNZ,CONB1-1    ;CONTINUE UNTIL Q = 0
;
    DW    TPOP        ;THEN DROP QUOTIENT
    DW    ZERO        ;STORE BYTE IN FIRST
    DW    NBUFR,POKEB    ;BYTE OF BUFFER
;
CONB2:    DW    DUP,NEGONE    ;TEST FOR END OF STRING
    DW    IFEQ,CONB3-1    ;IF YES
    DW    NBUFR,PEEKB    ;ELSE, INCREMENT BYTE COUNT
    DW    INC
    DW    NBUFR,POKEB
    DW    TPUSH,'0',TADD    ;CONVERT DIGIT TO ASCII
                ;AND STORE IN NEXT LOCATION
    DW    NBUFR
    DW    NBUFR,PEEKB,TADD
    DW    POKEB
    DW    JUMP,CONB2-1    ;REPEAT
;
CONB3:    DW    TPOP        ;DROP END OF STRING MARKER
    DW    NBUFR        ;PUSH RETURN BUFFER ADDRESS
    DW    TRET        ;AND RETURN
;
NBUFR:    DW    VARIABLE    ;THREADED VARIABLE
    DS    10        ;PLENTY LONG ENOUGH
;
; CONAXB - convert ASCII decimal string to binary
; ENTRY: TOP   - pointer to string
; EXIT:  TOP   - -1 if converted to binary
;          0 if not
;     TOP-1 - value of number if converted
;         ptr to string if not
; DESCRIPTION: converts only positive, unsigned
; integers. WRitten in assembly because I had it around
; and didn't want to rewrite it in threaded code.
;
CONAXB: DW    $+2        ;CODE
    POP    D        ;GET STRING POINTER
    PUSH    D        ;BUT LEAVE ON STACK
    LDAX    D        ;GET BYTE COUNT
    MOV    B,A
    LXI    H,0        ;STARTING VALUE
;
CONA1:    INX    D
    LDAX    D        ;GET NEXT CHARACTER
    CPI    '0'        ;TEST FOR DIGIT
    JC    CONAX        ;IF NOT
    CPI    '9'+1
    JNC    CONAX        ;IF NOT
    SUI    '0'        ;CONVERT TO BINARY
    PUSH    D        ;SAVE POINTER
    DAD    H        ;MULTIPLY CURRENT VALUE BY 10
    PUSH    H
    DAD    H
    DAD    H
    POP    D
    DAD    D
    MOV    E,A        ;ADD NEW BINARY DIGIT
    MVI    D,0
    DAD    D
    POP    D        ;RESTORE POINTER
    DCR    B        ;DEC COUNT
    JNZ    CONA1        ;CONTINUE TILL DONE
    POP    D        ;THEN DROP POINTER
    PUSH    H        ;PUSH NUMBER
    LXI    H,-1        ;AND -1
    PUSH    H
    JMP    NEXT
;
CONAX:    LXI    H,0        ;FAILURE: PUSH A ZERO
    PUSH    H
    JMP    NEXT
;
; DIV - 16 bit divide
; ENTRY: TOP   - divisor
;     TOP-1 - dividend
; EXIT:  TOP   - remainder
;     TOP-1 - quotient
; DESCRIPTION: performs a 32 bit by 16 bit division for
; positive integers only.  The quotient must be resolved
; in 16 bits.
;
DIV:    DW    $+2        ;CODE
    POP    B        ;BC <- DIVISOR
    POP    D        ;HLDE <- DIVIDEND
    LXI    H,0
    CALL    DIV1        ;DO DIVISION
    PUSH    D        ;PUSH QUOTIENT
    PUSH    H        ;PUSH REMAINDER
    JMP    NEXT
;
DIV1:    DCX    B        ;NEGATE BC
    MOV    A,B
    CMA
    MOV    B,A
    MOV    A,C
    CMA
    MOV    C,A
    MVI    A,16D        ;ITERATION COUNT
DIV2:    DAD    H        ;SHIFT HLDE
    PUSH    PSW        ;SAVE OVERFLOW
    XCHG
    DAD    H
    XCHG
    JNC    DIV3
    INR    L
DIV3:    POP    PSW        ;GET OVERFLOW
    JC    DIV5        ;IF OVERFLOW, FORCE SUBTRACTION
    PUSH    H        ;ELSE, SAVE DIVIDEND
    DAD    B        ;ATTEMPT SUBTRACTION
    JC    DIV4        ;IF IT GOES
    POP    H        ;ELSE RESTORE DIVIDEND
    JMP    DIV6
DIV4:    INR    E        ;INCREMENT QUOTIENT
    INX    SP        ;DROP OLD DIVIDEND
    INX    SP
    JMP    DIV6
DIV5:    DAD    B        ;FORCE SUBTRACTION
    INR    E        ;INC QUOTIENT
DIV6:    DCR    A        ;DECREMENT COUNT
    JNZ    DIV2        ;REPEAT UNTIL DONE
    RET
;
; The Names in the dictionary
; Notice that the actual printed names are chosen for typing
; convenience and do not necessarily match the internal names,
; which must conform to the assembler's rules. Also, not all
; functions have been included here.
;
NAMEBEG EQU    $
;
    DB    1,'+'
    DW    TADD
;
    DB    1,'-'
    DW    TSUB
;
    DB    4,'/MOD'
    DW    DIV
;
    DB    7,'EXECUTE'
    DW    EXECUTE
;
    DB    5,'CLEAR'
    DW    CLEAR
;
    DB    5,'MATCH'
    DW    MATCH
;
    DB    6,'LOOKUP'
    DW    LOOKUP
;
    DB    4,'EXEC'
    DW    EXEC
;
    DB    6,'MEMORY'
    DW    MEMORY
;
    DB    6,'CONBXA'
    DW    CONBXA
;
    DB    3,'INC'
    DW    INC
;
    DB    3,'DEC'
    DW    DEC
;
    DB    5,'MINUS'
    DW    MINUS
;
    DB    5,'PEEKW'
    DW    PEEKW
;
    DB    5,'PEEKB'
    DW    PEEKB
;
    DB    5,'POKEW'
    DW    POKEW
;
    DB    5,'POKEB'
    DW    POKEB
;
    DB    3,'POP'
    DW    TPOP
;
    DB    4,'SWAP'
    DW    SWAP
;
    DB    3,'DUP'
    DW    DUP
;
    DB    5,'FIRST'
    DW    FIRST
;
    DB    0            ;END OF DICTIONARY
;
NAMEEND EQU    $-1
;
DICSIZE EQU    NAMEEND-NAMEBEG+1    ;DICTIONARY SIZE IN BYTES
;
; Initialition Code
; Executed on start up of system but eventually overwritten by
; the expanding dictionary
;
; DICMOVE - moves the dictionary names
;        to the top of available memory
;
; <<<===  Modified For CPM initialization (RGF)  ===>>>
;
DICMOVE:
    LHLD    6
    SHLD    MEMORY+2    ;INIT TOP OF MEMORY
    XCHG            ;DE <- TOP OF MEMORY
    LXI    H,NAMEEND    ;HL <- SOURCE (END OF NAMES)
    LXI    B,DICSIZE    ;BC <- BYTE COUNT
                ;TRANSFER LOOP
DIC1:    MOV    A,M        ;GET NEXT BYTE
    STAX    D        ;MOVE IT
    DCX    H        ;DEC SOURCE POINTER
    DCX    D        ;DEC TARGET POINTER
    DCX    B        ;DEC COUNT
    MOV    A,B        ;TEST FOR ZERO
    ORA    C
    JNZ    DIC1        ;NOT YET
;
    XCHG            ;SET DICTIONARY VARIABLE
    INX    H
    SHLD    NAMES+2
;
    LDA    2        ;MODIFIY I/O ROUTINES
    STA    VCOUT+2     ;  SO THEY WILL WORD
    STA    VCIN+2        ; IN ANY SIZE CPM SYSTEM
;
    RET
;
;
;
;
    END    BASE